mgcp: Set net_end audio params in recvonly mode

Currently, if there is no SDP data in the MGCP message received from
the net, the fields containing audio encoding information are not set
in net_end. So in recvonly mode transcoding would not be set up
correctly.

This patch changes the implementation of the code handling CRCX and
MDCX to use the codec signalled in the MGCP local connection options
(field 'a:') if there isn't any SDP data. This is only halfway
negotiation, because the codec is used blindly and not matched
against the supported ones.

Sponsored-by: On-Waves ehf

4 files changed, 51 insertions, 3 deletions

diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index 9f0c0f9e2..2b44e40be 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -123,6 +123,7 @@ struct mgcp_rtp_tap {
 
 struct mgcp_lco {
 	char *string;
+	char *codec;
 	int pkt_period_min; /* time in ms */
 	int pkt_period_max; /* time in ms */
 };
diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index 21b9ff0f8..f0457d1aa 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -80,6 +80,8 @@ char *strline_r(char *str, char **saveptr)
 #define DEFAULT_RTP_AUDIO_DEFAULT_RATE  8000
 #define DEFAULT_RTP_AUDIO_DEFAULT_CHANNELS 1
 
+#define PTYPE_UNDEFINED (-1)
+
 static void mgcp_rtp_end_reset(struct mgcp_rtp_end *end);
 
 struct mgcp_parse_data {
@@ -598,7 +600,8 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 	talloc_free(rtp->audio_name);
 	rtp->audio_name = NULL;
 
-	rtp->payload_type = payload_type;
+	if (payload_type != PTYPE_UNDEFINED)
+		rtp->payload_type = payload_type;
 
 	if (!audio_name) {
 		switch (payload_type) {
@@ -614,7 +617,7 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 	}
 
 	if (sscanf(audio_name, "%63[^/]/%d/%d",
-		   audio_codec, &rate, &channels) < 2)
+		   audio_codec, &rate, &channels) < 1)
 		return -EINVAL;
 
 	rtp->rate = rate;
@@ -630,6 +633,20 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 		rtp->frame_duration_den = DEFAULT_RTP_AUDIO_FRAME_DUR_DEN;
 	}
 
+	if (payload_type < 0) {
+		payload_type = 96;
+		if (rate == 8000 && channels == 1) {
+			if (!strcmp(audio_codec, "GSM"))
+				payload_type = 3;
+			else if (!strcmp(audio_codec, "PCMA"))
+				payload_type = 8;
+			else if (!strcmp(audio_codec, "G729"))
+				payload_type = 18;
+		}
+
+		rtp->payload_type = payload_type;
+	}
+
 	if (channels != 1)
 		LOGP(DMGCP, LOGL_NOTICE,
 		     "Channels != 1 in SDP: '%s'\n", audio_name);
@@ -801,9 +818,12 @@ static int parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
 static void set_local_cx_options(void *ctx, struct mgcp_lco *lco,
 				 const char *options)
 {
-	char *p_opt;
+	char *p_opt, *a_opt;
+	char codec[9];
 
 	talloc_free(lco->string);
+	talloc_free(lco->codec);
+	lco->codec = NULL;
 	lco->pkt_period_min = lco->pkt_period_max = 0;
 	lco->string = talloc_strdup(ctx, options ? options : "");
 
@@ -811,6 +831,10 @@ static void set_local_cx_options(void *ctx, struct mgcp_lco *lco,
 	if (p_opt && sscanf(p_opt, "p:%d-%d",
 			    &lco->pkt_period_min, &lco->pkt_period_max) == 1)
 		lco->pkt_period_max = lco->pkt_period_min;
+
+	a_opt = strstr(lco->string, "a:");
+	if (a_opt && sscanf(a_opt, "a:%8[^,]", codec) == 1)
+		lco->codec = talloc_strdup(ctx, codec);
 }
 
 void mgcp_rtp_end_config(struct mgcp_endpoint *endp, int expect_ssrc_change,
@@ -955,6 +979,9 @@ mgcp_header_done:
 						tcfg->audio_fmtp_extra);
 	if (have_sdp)
 		parse_sdp_data(&endp->net_end, p);
+	else if (endp->local_options.codec)
+		set_audio_info(p->cfg, &endp->net_end,
+			       PTYPE_UNDEFINED, endp->local_options.codec);
 
 	if (p->cfg->bts_force_ptime) {
 		endp->bts_end.packet_duration_ms = p->cfg->bts_force_ptime;
@@ -1012,6 +1039,7 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 	struct mgcp_endpoint *endp = p->endp;
 	int error_code = 500;
 	int silent = 0, osmux = 0;
+	int have_sdp = 0;
 	char *line;
 	const char *local_options = NULL;
 
@@ -1058,6 +1086,7 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 			break;
 		case '\0':
 			/* SDP file begins */
+			have_sdp = 1;
 			parse_sdp_data(&endp->net_end, p);
 			/* This will exhaust p->save, so the loop will
 			 * terminate next time.
@@ -1088,6 +1117,10 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 	set_local_cx_options(endp->tcfg->endpoints, &endp->local_options,
 			     local_options);
 
+	if (!have_sdp && endp->local_options.codec)
+		set_audio_info(p->cfg, &endp->net_end,
+			       PTYPE_UNDEFINED, endp->local_options.codec);
+
 	setup_rtp_processing(endp);
 
 	/* policy CB */
@@ -1462,6 +1495,8 @@ void mgcp_free_endp(struct mgcp_endpoint *endp)
 
 	talloc_free(endp->local_options.string);
 	endp->local_options.string = NULL;
+	talloc_free(endp->local_options.codec);
+	endp->local_options.codec = NULL;
 
 	mgcp_rtp_end_reset(&endp->bts_end);
 	mgcp_rtp_end_reset(&endp->net_end);
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index 53884833f..19615d9da 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -168,6 +168,12 @@ static void test_strline(void)
 		 "a=rtpmap:99 AMR/8000\r\n"	\
 		 "a=ptime:40\r\n"
 
+#define MDCX4_RO "MDCX 18983221 1@mgw MGCP 1.0\r\n" \
+		 "M: recvonly\r"		\
+		 "C: 2\r\n"          \
+		 "I: 1\r\n"                    \
+		 "L: p:20, a:AMR, nt:IN\r\n"
+
 #define SHORT2	"CRCX 1"
 #define SHORT2_RET "510 000000 FAIL\r\n"
 #define SHORT3	"CRCX 1 1@mgw"
@@ -258,6 +264,7 @@ static const struct mgcp_test tests[] = {
 	{ "MDCX4_PT2", MDCX4_PT2, MDCX4_RET("18983218"), 99, 126 },
 	{ "MDCX4_PT3", MDCX4_PT3, MDCX4_RET("18983219"), 99, 126 },
 	{ "MDCX4_SO", MDCX4_SO, MDCX4_RET("18983220"), 99, 126 },
+	{ "MDCX4_RO", MDCX4_RO, MDCX4_RET("18983221"), PTYPE_IGNORE, 126 },
 	{ "DLCX", DLCX, DLCX_RET, -1, -1 },
 	{ "CRCX_ZYN", CRCX_ZYN, CRCX_ZYN_RET, 97, 126 },
 	{ "EMPTY", EMPTY, EMPTY_RET },
diff --git a/openbsc/tests/mgcp/mgcp_test.ok b/openbsc/tests/mgcp/mgcp_test.ok
index 3901cfbed..7301a8152 100644
--- a/openbsc/tests/mgcp/mgcp_test.ok
+++ b/openbsc/tests/mgcp/mgcp_test.ok
@@ -49,6 +49,11 @@ Testing MDCX4_SO
 Detected packet duration: 40
 Requested packetetization period: 20-20
 Connection mode: 2: SEND
+Testing MDCX4_RO
+Dummy packets: 1
+Packet duration not set
+Requested packetetization period: 20-20
+Connection mode: 1: RECV
 Testing DLCX
 Detected packet duration: 20
 Requested packetization period not set